The mixing or agitation of materials, such as concrete, in, for example, a rotary mixer, presents an extremely wearing, abrasive environment. The control and reduction of wear of parts and materials exposed to such environment is of particular interest, for example, the concrete or cement industry. For example, cement trucks having rotary drum mixers, have been a particular focus of attention to the problem of reducing internal wear. One approach to the problem of reducing wear, in a rotary mixer is to line it or coat it with a suitable material. Portable rotary mixers have been lined with, for example, a polyurethane and rubber. Another approach has been to use a polymeric material such as polyurethane, the polymer having dispersed therewithin, a wear-resistant material. Examples of such wear-resistant materials dispersed within a coating would be ceramic tiles or ceramic chips.
One of the problems with utilization of coatings, as described above, is that when the coatings become worn the underlying substrate, which is usually metal, then is exposed to the abrasive, often corrosive material being mixed. Further, once the polymeric coating has been perforated, the ability of the abrasive material to erode the somewhat more abrasion susceptible material thereunder is enhanced. With the coating removed, the underlying metal infrastructure is deferentially worn to the exclusion of the coating.
The problems encountered in employing a coated-interior rotary or rotatable drum mixer is particularly acute for mixing fins deployed within such rotary drums. Mixing fins provide agitation so that material rotating within the mixing drums may be intimately co-mingled. In this manner, the mixing process is enhanced to provide a uniformly, mixed composition, e.g., concrete. Mixing fins are exposed to an even more aggressively eroding and corroding function of the mixer in that the mixing fin is intended to create turbulence and agitation within the materials to be mixed as well as transporting the material e.g., for delivery. As such, mixing fins then require regular replacement in order to maintain their efficacy.
Urethane coated, metal mixing fins have been employed in the prior art. Such fins comprise a substantially metallic upstanding member or backing member, with a urethane coating thereon. Coated metal fins present a particularly difficult problem at time of fin replacement. Coated metallic fins were normally welded to the interior wall rotary mixer. Welding would be accomplished by having the welder physically work within the substantially closed rotary mixer drum. At replacement, the heat of the welding process tends to cause some of the polymeric coating material to vaporize to create an atmosphere which was not particularly healthy for the welder to inhale.
The present invention overcomes the problem of the above prior art and provides an enhanced or improved mixing fin particularly adaptable and useful within large rotary mixers, such as those employed on cement mixer trucks.